Gu Kailai, the wife of an ex-Communist Party official, is accused of killing a British businessman, Neil Heywood.

The microblog is closely watched by the authorities because its users often discuss sensitive topics.

Issues with posting appeared to have lasted for about an hour. Sina blamed "a technical error".

In March, the Chinese government made Sina Weibo disable the microblog's commenting function for several days after posts about rumours of a military coup.

Ms Gu's trial has now ended - a verdict will be announced later - and Weibo appears to be back to normal. But on Sina.com portal, users are still not able to get results by searching for the name "Gu Kailai".

Instead, a message is displayed: "According to the relevant laws and policies, search results for #Gu Kailai are not shown."

Shortly after the start of the trial @GreatFireChina wrote on Twitter: "No one can post anything on Weibo now as the input space just disappeared. FYI: Gu Kailai murder trial begins."

Some users found a way to discuss the case by referring to Ms Gu by her initials.

Image caption
Ms Gu is accused of poisoning Mr Heywood in Chongqing last year

"Impossible to post #gukailai trial news on Weibo. Finally succeeded with her initials GKL. Let's see how long it'll take censors to delete," wrote @LiYuan6.

She later mentioned that the microblog would not allow her to repost messages about the trial, written by Sina Weibo's "own official news account and Xinhua's official account".

Disappearing posts

Other Chinese microblogging services QQ Weibo and Sohu Weibo do not seem to have suffered as much censorship, although some users have mentioned that their posts had been removed.

"QQ.com removed my posting! Some department must have made the decision [to remove it]; so I give up, no more reposting on the trial," wrote QQ Weibo user Jing Gege.

Several users criticised the government and the trial, which was closed to the public.

"Trial of the century, five factors: appointed court, appointed judge, appointed lawyers, pre-determined crimes and foregone conclusions," wrote a QQ Weibo member called Chaoge.

On Sohu Weibo, user Sanfenzhongde posted: "Outside the court house, Chinese and foreign journalists are stopped behind the cordon lines 50m away [from the court room], and there are a lot of policemen around."

A court official told reporters Ms Gu, whose husband Bo Xilai was the Communist Party head in Chongqing, had not contested the charge that she had killed Mr Heywood by poisoning in 2011.